The present invention relates to a technique for checking operation of a speaker.
In cases where a speaker is used in a concert venue, a theater, or the like, it is common to check operation of the speaker before and/or after use of the speaker. “before and/or after use of the speaker” in a concert venue means, for example, before the start of an actual performance, which is a main feature of the day, in the concert (namely, during preparation for the actual performance) and/or after the end of the concert.
“check operation of the speaker” includes examining whether or not any abnormality, such a failure or another trouble, has occurred in the speaker. Examples of such a speaker abnormality include a disconnection, a short-circuit, a temperature rise of the voice coil, breakage of the cone paper, breakage of the speaker edge, aged deterioration, and the like.
Heretofore, there have been known various speaker operation checking methods. As one example, it has been known to detect an abnormality of a speaker by measuring impedance of the speaker. This speaker operation checking method is arranged to detect, via sensors, an output voltage and an output current between an amplifier output and the speaker, measure impedance on the basis of the detected output voltage and the detected output current, compare the measured impedance and a predetermined value, and then detect an abnormality of the speaker on the basis of a result of the comparison (see, for example, Patent Literature 1 identified below).
However, the conventional technique disclosed in Patent Literature 1 or the like, which is arranged to check the operation of the speaker basically by inputting to the speaker a test signal (such as high-frequency noise) dedicated to the speaker operation checking, is never suited for checking the operation of the speaker during full-scale use of the speaker, such as during an actual performance in the concert. In Patent Literature 1, it is suggested that in a disaster-preventing system, the operation of the speaker can be checked during use of the speaker by mixing the above-mentioned test signal into a sound signal to be input to the speaker. However, even where such a test signal is a signal of a high frequency range difficult for the human ears to hear, it is not preferable at all that the test signal mix into a sound generated from a speaker, in an application where high sound quality of sounds generated from speakers is required, such as in a full-scale speaker system employed in a concert hall or the like. Thus, with the conventional technique, it is not possible to perform a process for detecting an abnormality of a speaker in the middle of, and concurrently with, full-scale use of the speaker, for example, in an application where high audio quality of a sound generated from the speaker is required. Further, with the conventional technique, it is not possible to predict, or know beforehand, occurrence of a failure of the speaker before a failure actually occurs during use of the speaker.
Furthermore, in a speaker system where a plurality of types of speaker units are housed in a single enclosure, such as a “two-way speaker” where two types of speaker units, like a high-frequency-rage (tweeter) speaker and a mid-and-low-frequency-range (mid-bass) speaker, are housed in a single enclosure, the conventional technique disclosed in Patent Literature 1 or the like cannot detect a speaker abnormality while discriminating which one of the speaker units in the enclosure has failed.
Patent Literature 1: Japanese Patent Application Laid-open Publication No. HEI-9-307988